Simplify the following expression: $\sqrt{40} - \sqrt{10}$
Explanation: First, try to factor any perfect squares out of the radicals. $= \sqrt{40} - \sqrt{10}$ $= \sqrt{4 \cdot 10} - \sqrt{10}$ Separate the radicals and simplify. $= \sqrt{4} \cdot \sqrt{10} - \sqrt{10}$ $= 2\sqrt{10} - \sqrt{10}$ Finally, simplify by combining the terms. $= ( 2 - 1 )\sqrt{10} = \sqrt{10}$